Author Topic: SVM-45 and SVM-140 jig centering bushing  (Read 120 times)

Offline jvh

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SVM-45 and SVM-140 jig centering bushing
« on: March 15, 2019, 11:28:24 pm »
Hello everyone,

as many others I had a problem with knife centering in jig SVM-45 and SVM-140, because jig does not center the knife correctly and bevel on one side is different from other side.

Therefore I made a centering bushing which is mounted on the jig. Bushing is eccentric and by turning left or right is a knife easily centered. Outside diameter is 15,3 mm, inside 12+0,1, eccentricity ca 1,6 mm, length 25 mm, lock screw M3x3, 5 mm from the end.

Outside diameter is still small to use adjustable stop without any limitation, moreove there can be a gap between the bushing and  adjustable stop (theoreticaly up to 6 mm), which allows to make angle corrections by turning adjustable stop. For angle checking I'm using Anglemaster WM-200 on opposite sides of blade.

jvh


Offline Ken S

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #2 on: March 16, 2019, 03:14:53 am »
JVH,

Your idea is intriguing. It will take me a while to wrap my head around it, however, I do think you are on to something significant.

Good work!

Ken

Offline SHARPCO

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #3 on: March 16, 2019, 11:06:46 am »
Good idea!

Offline RichColvin

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #4 on: March 16, 2019, 12:34:04 pm »
Jan,

I’ve wanted to use the SVM-00 Small Knife Holder with pocket knives which have small blades, but the ones I sharpen always have multiple blades on each side.  This made the angles drastically different for each side.

And I’ve found that most small blades are too small for the SVM-45 to hold.

I think that a greatly exaggerated version your cam could make this work!   I’m thinking maybe this would need 7-10 mm difference side to side (I.e., 12 mm hole with 20-25 mm outside diameter).

I’m going to make one in the next few weeks.   I’ll let you know what I find. 

Brilliant idea !   I’m excited.

Kind regards,
Rich


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Offline Jan

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #5 on: March 16, 2019, 02:57:33 pm »
Congrats jvh! Really brilliant idea!  :) Thanks for sharing it here.

I could imagine some ticks on the eccentric bushing surface which will help to mount a knife with specific blade thickness.

Jan

Offline jvh

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #6 on: March 16, 2019, 07:09:17 pm »
Thanks all!  :)

I forgot to mention one disadvantage - when grinding and raising the handle at the end, the jig axis and therefore grinding angle changes a little bit, due eccentricity of the bushing. It's not a problem for me in the most cases because eccentricity isn't too big and method with jig 's rotation left/right is usable without any influence to grinding angle.

Quote from: RichColvin
I’ve wanted to use the SVM-00 Small Knife Holder with pocket knives which have small blades, but the ones I sharpen always have multiple blades on each side.  This made the angles drastically different for each side.
See above - with high eccentricity there is a risk of high angle changes when raising the handle of the knife.

For such knives I'm using correction by turning adjustable stop. Set one side with Anglemaster WM-200, mark start position of adjustable stop, turn the jig and set the same angle on the other side by rotation of the adjustable stop. Count the number of turns, write this number to blade (e.g +2,5) and mark finish position of of adjustable stop. Now, when I'm turning the jig I make angle correction by turning adjustable stop to start or finish position. It's not comfortable at all but it works. :)


Quote from:  Jan
Thanks for sharing it here.
I could imagine some ticks on the eccentric bushing surface which will help to mount a knife with specific blade thickness.
Not here only, see knife.cz  ;)
It's not that easy, the clamps would always have to be in the same position (e.g. paralel), otherwise angle will differ.

« Last Edit: March 16, 2019, 07:42:03 pm by jvh »

Offline Ken S

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Re: SVM-45 and SVM-140 jig centering bushing
« Reply #7 on: March 16, 2019, 11:04:31 pm »
JVH,

I would like to share some thoughts based on your clever new collar idea.

First, let's imagine one of Jan's drawings of a knife jig with an axis line drawn through it. This represents a jig with a knife attached which is perfectly centered and aligned.

Next we add the wooden block used by Wootz in his knifegrinders.vom.au you tubes to hold the knife and jig to measure Projection. The jig and knife must lay on the block with Jan's center axis line parallel to the block.

If everything is aligned properly, the edge lines for both sides would fall into the same kerf line on the sliding block.

If the two kerf lines do not match, and can be made to match by revolving the eccentric cam, this would be a major advance!!!

Ken

ps I started this earlier today and just read John's last post after I was going to post this. It sounds like there are some tweaks needed, however, I believe the effort eill be most eorthehile.